1. Field of the Invention
This invention relates to a system having a plurality of "fluid beds" as found in hospitals or the like. Fluid beds are formed of fine beads which flow when pressurized air jets upwardly through the beads from a diffusion board under the beads. When the beads are fluidized, a human body may be held by the beads in a floating manner on the bed for medical treatment or the like.
2. Description of the Related Art
FIG. 5(A) is a sectional view showing the construction of a conventional fluid bed and FIG. 5(B) is a sectional view showing the fluid bed in operation. Fluid beds of the type shown in FIG. 5 are often operated in groups.
Referring to FIG. 5(A), an air supplying device 9, comprising a ring compressor, is adapted to receive air from outside, pressurize the air and supply the air thus pressurized into a closed chamber 3. The pressurized air, the temperature of which has been raised by the pressurizing operation of the air supplying device 9, is cooled down to a predetermined temperature by a heat exchanger 11 provided in the pressurized air-supplying path. A cooling fan 10 is provided for supplying heat exchanging air to the heat exchanger 11. In the closed chamber 3, the pressurized air Al supplied thereto through an air duct D from the heat exchanger is spread under a diffusion board 2. The diffusion board 2 is a plate made of porous material. The pressurized air A1 in the closed chamber 3 is exuded and diffused, as exudation air A2, through a large number of fine holes in the diffusion board 2. A mattress 4 which is formed from fine particles such as beads 4a which are caused to flow by the exudation air A2. The mattress will be referred to as "the bead mattress 4," when applicable. A cloth sheet S whose mesh is smaller than the size of the beads covers the upper surface of the bead mattress. The exudation air A2 can pass through the cloth sheet S, while the beads 4a are contained by the sheet S, i.e., the provision of the cloth sheet S prevents the beads 4a from scattering outside the fluid bed body 1.
Further in FIG. 5(A), bead pipes 5 and 7 are provided for supplying beads into the bead mattress or for removing the beads therefrom, and a bead valve 6 is provided for opening and closing the bead pipes 5 and 7.
Use of a fluid bed can prevent the blood circulatory disturbance which may occur when the human body is locally pressed. Therefore, fluid beds are used for accelerating the regeneration of the skin of patients who have been heavily burnt, or for preventing "bedsores" on long-term bedridden patients. When on the bead mattress 4, the patient's whole body is supported by substantially uniform pressures, such that the body surface pressure at individual pressure points is minimized. Accordingly, the pressure applied to the skin is reduced. In addition, because the fluctuation in pressure distribution is small, blood circulatory disturbance which may be caused when a vein is pressed is prevented.
FIG. 5(B) shows an example of a human body supported, in a floating manner, on the fluid bed of FIG. 5(A). The human body BH is supported on the bead mattress 4 such that the body sinks in the mattress to the maximum extent allowed by the medical treatment. The equivalent specific gravity of the bead mattress when the beads are flowing is about 1.29 under which condition the body BH sinks as shown in FIG. 5(B). Accordingly, as the body sinks in the bead mattress 4, the human body BH is supported by a larger contact area thereby reducing the body surface pressure.
Fluid beds are operated according to two methods: (1) a continuous fluidizing method, and (2) an intermittent fluidizing method.
Method (1) is the ordinary operating method according to which the air supplying device 9 is continously operated to continuously fluidize the beads 4a.
Method (2) is used to prevent the unsuitable movement of the body, as is done with the application of plaster-bandage to prevent the skin from being locally pressed. When the flow of the beads is stopped, the body is caused to sink substantially in the bead mattress 4 so that the bead mattress acts as if it were a plaster-bandage. The beads 4a are fluidized intermittently so that the local pressure on the skin which builds while the beads are not flowing is intermittently eliminated.
In general, a number of fluid beds are installed in a hospital or the like. Because fluid beds, as shown in FIG. 5, have their own air supplying devices, the following problems are associated with their operation:
(1) Vibration and audible noise from the air supplying device 9 is transmitted to the patient on the bed and to other persons in the same room as the patient.
(2) The height of the fluid bed is increased by the size of the air supplying device 9, making it difficult for a person to get on and off the bed. This problem is especially serious because fluid beds are used primarily for medical treatment.
(3) The bed itself is heavy, and therefore it is difficult to move.
(4) The electric power requirements of the bed's air supplying device are large. Therefore, it is impossible to use a number of fluid beds in rooms with ordinary wiring of limited capacity.
(5) The bed's air supplying device comprises an electric motor. The electronic noise from the electric motor may cause other electrical equipment in the same room to operate improperly.
(6) When a number of fluid beds are used, a number of air supplying devices are employed resulting in a high total installation cost.
(7) The bed's air supplying device requires an electric source with respect to which safety measures must be provided so that the bed is safe as a medical appliance at all times.
Thus, there is a need for a fluid bed system in which vibration and noise of individual fluid beds is small, in which individual bed heights can be changed so that a person may readily get off and on the bed, and in which the weight of each bed is small. Further, there is a need for a fluid bed system in which no motor is placed in the room where the fluid bed is provided so that supplemental electric capacity is not required in the room and so that electric motor noise will not interfere with other instruments in the room. Finally, there is a need for a fluid bed system in which the number of expensive air supplying devices is smaller than the number of fluid beds.